Alan Kimura

A phase II/III clinical study of enzyme replacement therapy with idursulfase in mucopolysaccharidosis II (Hunter syndrome)

Purpose: To evaluate the safety and efficacy of recombinant human iduronate-2-sulfatase (idursulfase) in the treatment of mucopolysaccharidosis II.Methods: Ninety-six mucopolysaccharidosis II patients between 5 and 31 years of age were enrolled in a double-blind, placebo-controlled trial. Patients were randomized to placebo infusions, weekly idursulfase (0.5 mg/kg) infusions or every-other-week infusions of idursulfase (0.5 mg/kg). Efficacy was evaluated using a composite endpoint consisting of distance walked in 6 minutes and the percentage of predicted forced vital capacity based on the sum of the ranks of change from baseline.Results: Patients in the weekly and every-other-week idursulfase groups exhibited significant improvement in the composite endpoint compared to placebo (P = 0.0049 for weekly and P = 0.0416 for every-other-week) after one year. The weekly dosing group experienced a 37-m increase in the 6-minute-walk distance (P = 0.013), a 2.7% increase in percentage of predicted forced vital capacity (P = 0.065), and a 160 mL increase in absolute forced vital capacity (P = 0.001) compared to placebo group at 53 weeks. Idursulfase was generally well tolerated, but infusion reactions did occur. Idursulfase antibodies were detected in 46.9% of patients during the study.Conclusion: This study supports the use of weekly infusions of idursulfase in the treatment of mucopolysaccharidosis II.

Long-term, open-labeled extension study of idursulfase in the treatment of Hunter syndrome

Purpose: This study evaluated the safety and effectiveness of long-term enzyme replacement therapy with idursulfase (recombinant human iduronate-2-sulfatase) in patients with Hunter syndrome.Methods: All 94 patients who completed a 53-week double-blinded study of idursulfase enrolled in this open-labeled extension study and received intravenous idursulfase at a dose of 0.5 mg/kg weekly for 2 years, and clinical outcomes and safety were assessed.Results: No change in percent predicted forced vital capacity was seen, but absolute forced vital capacity demonstrated sustained improvement and was increased 25.1% at the end of the study. Statistically significant increases in 6-minute walking test distance were observed at most time points. Mean liver and spleen volumes remained reduced throughout the 2-year extension study. Mean joint range of motion improved for the shoulder and remained stable in other joints. Both the parent- and child-assessed Child Health Assessment Questionnaire Disability Index Score demonstrated significant improvement. Infusion-related adverse events occurred in 53% of patients and peaked at Month 3 of treatment and declined thereafter. Neutralizing IgG antibodies were detected in 23% of patients and seemed to attenuate the improvement in pulmonary function.Conclusions: Weekly infusions of idursulfase result in sustained clinical improvement during 3 years of treatment.

Development of idursulfase therapy for mucopolysaccharidosis type II (Hunter syndrome): the past, the present and the future

Mucopolysaccharidosis type II (MPS II; Hunter syndrome; OMIM 309900) is a rare, multisystemic, progressive lysosomal storage disease caused by deficient activity of the iduronate-2-sulfatase (I2S) enzyme. Accumulation of the glycosaminoglycans dermatan sulfate and heparan sulfate results in a broad range of disease manifestations that are highly variable in presentation and severity; notably, approximately two-thirds of individuals are affected by progressive central nervous system involvement. Historically, management of this disease was palliative; however, during the 1990s, I2S was purified to homogeneity for the first time, leading to cloning of the corresponding gene and offering a means of addressing the underlying cause of MPS II using enzyme replacement therapy (ERT). Recombinant I2S (idursulfase) was produced for ERT using a human cell line and was shown to be indistinguishable from endogenous I2S. Preclinical studies utilizing the intravenous route of administration provided valuable insights that informed the design of the subsequent clinical studies. The pivotal Phase II/III clinical trial of intravenous idursulfase (Elaprase®; Shire, Lexington, MA, USA) demonstrated improvements in a range of clinical parameters; based on these findings, intravenous idursulfase was approved for use in patients with MPS II in the USA in 2006 and in Europe and Japan in 2007. Evidence gained from post-approval programs has helped to improve our knowledge and understanding of management of patients with the disease; as a result, idursulfase is now available to young pediatric patients, and in some countries patients have the option to receive their infusions at home. Although ERT with idursulfase has been shown to improve somatic signs and symptoms of MPS II, the drug does not cross the blood–brain barrier and so treatment of neurological aspects of the disease remains challenging. A number of novel approaches are being investigated, and these may help to improve the care of patients with MPS II in the future.

Development and validation of the angiotensin-converting enzyme inhibitor (ACEI) induced angioedema investigator rating scale and proposed discharge criteria

BackgroundThe use of angiotensin-converting enzyme inhibitors (ACEI) has been associated with the development of bradykinin-mediated angioedema. With ever-widening indications for ACEI in diseases including hypertension, congestive heart failure and diabetic nephropathy, a concomitant increase in ACEI-Angioedema (ACEI-A) has been reported. At present there is no validated severity scoring or discharge criteria for ACEI-A. We sought to develop and validate an investigator rating scale with corresponding discharge criteria using clinicians experienced in treating ACEI-A.MethodsIn-depth, 60-min qualitative telephone interviews were conducted with 12 US-based emergency physicians. Beforehand, clinicians were sent four case studies describing patients experiencing different severities of angioedema attacks. Clinicians were initially asked open-ended questions about their experience of patients’ symptoms, treatment and discharge decisions. Clinicians then rated each patient case study and discussed patient diagnoses, ratings of symptom severity and discharge evaluation. The ratings were used to assess inter-rater reliability of the scale using the intra-class correlation coefficient (ICC) using IBM SPSS analysis Version 19 software.ResultsThe findings provide support focusing on four key symptoms of airway compromise scored on a 0–4 scale: 1) Difficulty Breathing, 2) Difficulty Swallowing, 3) Voice Changes and 4) Tongue Swelling and the corresponding discharge criteria of a score of 0 or ‘No symptoms’ for Difficulty Breathing and Difficulty Swallowing and a score of 0 or 1 indicating mild or absence of symptoms for Voice Change and Tongue Swelling. Eleven clinicians agreed the absence of standardized discharge criteria supported the use of this scale. All physicians concurred with the recommended discharge criteria. The clinician ratings provided evidence of strong inter-rater reliability for the rating scale (ICC > 0.80).ConclusionThe investigator rating scale and discharge criteria are clinically valid, relevant and reliable. Moreover, both address the current unmet need for standardized ED discharge criteria.